The invention relates to refills for writing, drawing and/or painting devices based on polymeric binders, and to a method for its manufacture.
Polymer-bonded refills based on polymers derived from crude oil for writing, drawing and/or painting are known in principle.
The term “colored or graphite-based polymer-bonded refills for writing, drawing and/or painting” should be understood to mean on the one hand, refills which have been firmly fixed into wood or other materials which can be sharpened, and on the other hand, refills which are displaceably mounted in a rigid sheath. Examples in this regard are wooden pencils and refills for mechanical pencils, for example those known as retractable pencils or drop-action pencils. In this case, the refills usually have an external diameter in the range from approximately 0.3 mm to 6 mm. Refills of this type also include those known as woodless pencils, which are refills without a sheath.
Thus, for example, polymer-bonded colored and graphite refills are known from WO 2010/006742 A1. Refills of this type contain a polymeric binder, wax, palm oil and fillers.
The use of wax in refills of this type means on the one hand that the writing properties are affected, and on the other hand that the extrusion pressure when manufacturing the refills is reduced.
The disadvantage with refills of this type is that adding wax has a negative influence on the specific strength of the refills. It has been shown that the specific strength falls steadily with increasing wax content.
The waxes can be considered to have a negative influence on wetting of the fillers within the polymer matrix.